1. Field of the Invention:
The present invention relates to a method of growing semiconductor crystals, such as, for example, silicon or germanium crystals for use in the manufacture of semiconductor components and manufactured by the Czochralski method, and, more particularly, to a method of automatically controlling the diameter of such crystals to get a predetermined shape in the region from after making of seed through shouldering to a constant diameter of the body using a combination of new parameters and adjusting these parameters.
2. Description of the Prior Art:
The Czochralski method of crystal growing is well known and various schemes are available in the prior art for controlling the diameter of the crystal to desired values during the solidification both in the stages of shoulder and body. Such diameter control schemes have been of the closed loops variety and it has been well known to use an electrooptical system, for example. In a conventional method, while the temperature profile in the melt is kept constant, a crystal diameter related offset signal is supplied to a motor control means for the motor to pull the crystal at a desired diameter. The adjustment of the pulling velocity has adverse effects on the crystallinity of the resulting crystal, such as dislocations generated at the peripheral portion. In another conventional method, the diameter is controlled solely by way of adjusting the temperature profile to enlarge or lessen it through change in the power supplied to the surrounding heating means. Generally, the heat capacity of the melt is too large to allow temperature profile to be finely changed to a proper extent and with quick response, and diameter control is therefore unsuccessful in practical terms.